Blue rush, blue arrow rush, hard rush, incurved rush, Juncus glaucus Ehrhart

Juncus inflexus has rhizomes that can extend for 3–5 mm and produce smooth, cyclindrical stems ranging from 1.5–3 mm in diameter.
This species has pedicellate flowers (single multiflowered inflorescence per plant) with ovate bracteoles; the tepals (petals) are reddish brown, lance-like in shape, and can be 2.7–3.5 mm. The margins of the flowers are smooth. Flowers contain 6 stamens with filaments ranging from 0.8–1.5 mm and anthers ranging from 0.8–1 mm, and a style that is 0.3 mm long. Seeds are amber to brown, obliquely ovoid to oblong, not tailed, approximately 0.6 mm in length, and contain veins which are 0.3–0.5 mm. Diploid (2n) individuals have 20, 38, or 40 chromosomes.

Juncus inflexus typically blooms and fruits between June and September. While this species can produce viable seed, it primarily grows by rhizomal growth (Missouri Botanical Garden 2012).

Juncus inflexus is a hardy species that can tolerate urban pollution and will regrow if cut back to the root (Chalet Nursery 2012, Missouri Botanical Garden 2012). Under ideal conditions, J. inflexus can live up to 8 years (Chalet Nursery 2012).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic	Beneficial

Juncus inflexus has a moderate environmental impact in the Great Lakes.
Realized:
Once this species establishes in an ecosystem, it will likely persist (Stuckey 1981 in Vincent and Cusick 1998). In wetland environments, rushes will out-compete other plant species (Stevens and Hoag 2003).

Juncus inflexus tends to have a significant presence in the seed bank in areas of intensive agriculture (Reiné et al. 2004).

Potential:
Juncus gerardii poses a competitive threat to the native and naturalized Juncus spp. in the Great Lakes, especially those listed as threatened or endangered, including J. alpinus auct. non Vill., J. ambiguus Guss., J. balticus Willd., J. biflorus Elliot, J. marginatus Rostk. var. biflorus (Elliot) Alph. Wood, J. brachycarpus Engelm., J. brachycephalus (Engelm.) Buchenau, J. dichotomus Elliot, J. diffusissimus Buckley, J. ensifolius Wikstr., J. greenei Oakes & Tuck., J. interior Wiegand, J. militaris Bigelow, J. pelocarpus E. Mey., J. scirpoides Lam., J. secundus P. Beauv. ex Poir., J. stygius L., J. stygius L. ssp. americanus (Buchenau) Hultén, J. subcaudatus (Engelm.) Coville & S.F. Blake, J. vaseyi Engelm. (USDA NRCS 2012c).

Juncus inflexus also poses a genetic threat, because hybrids with J. effusus are possible when these species grow in the same location (Clifford 1958). Several species of this genus have synchronous flowering to attract pollinators, which creates potential for outcrossing (Michalski and Durka 2007).

In the United Kingdom, the roots of Juncus spp. have been observed to trap water and alter the hydrology in shallow water environments (Centre for Aquatic Plant Management 2004).

There is little or no evidence to support that Juncus inflexus has significant socio-economic impacts in the Great Lakes.
Realized:
Many Juncus spp. serve as a host for larvae of Coquillettidia, a genus of mosquitoes that can serve as a vector for various animal- and human-borne vectors (Sérandour et al. 2010).

Potential:
Juncus inflexus may be confused with or pose a competitive threat to native rushes that are culturally important, including J. arcticus ssp. littoralis and J. effusus (USDA NRCS 2012b).

There is little or no evidence to support that Juncus inflexus has significant beneficial effects in the Great Lakes.
Realized:
Juncus inflexus can be planted in rain gardens and for erosion control (Missouri Botanical Garden 2012).

After 20 days of exposure, J. inflexus was able to remove all 100 mg/L of ethylene glycol dinitrate (EGDN), an explosive ingredient in dynamite, from in vitro regenerants (Podlipná et al. 2010). However, when exposed to 500 mg/L, J. inflexus began to die (Podlipná et al. 2008).

Numerous animals feed on the seeds of rushes, including waterfowl, songbirds, quail, cottontail, muskrat (also feeds on roots and rhizomes), porcupine, and other small mammals (Martin 1951 in Stevens and Hoag 2003). Juncus spp. provide habitat for amphibians and various wetland birds, as well as spawning ground for some fish species (Stevens and Hoag 2003).

Potential:
Cattle, horses, and sheep will graze on Juncus spp., but their specific value as fodder is unknown (Centre for Aquatic Plant Management 2004, Cosyns et al. 2005).

The rhizome matrix can support numerous bacteria that are useful in wastewater treatment (Stevens and Hoag 2003).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
Biological
Aphids may occasionally feed on Juncus spp., but most rushes are fairly resilient to extensive damage from insect or diseases (Stevens and Hoag 2003). Cattle, horses, and sheep graze on Juncus spp., but the extent of control gained from grazing is unknown (Centre for Aquatic Plant Management 2004, Cosyns et al. 2005).

Physical
Juncus inflexus will regrow if it is cut or mowed; therefore, these methods will only provide control if done repeatedly (Missouri Botanical Garden 2012).
The rhizome matrix of Juncus spp. enables them to withstand periods of drought and flooding; water level fluctuation is not recommend as a physical control method (Stevens and Hoag 2003).

Chemical
Sethoxydim will target most grass species and should not affect nearby broadleaf herbs, sedges, or woody plants (IPAW 2012). Glyphosate and ammonium salt of imazapyr will control J. inflexus, but are non-selective and should be applied carefully (Centre for Aquatic Plant Management 2004). Glyphosate should be sprayed directly onto foliage in mid-late summer (Centre for Aquatic Plant Management 2004).

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.